If your website isn't mobile-ready, it may soon be invisible to those searching on Google. Luckily, we at Blue Wheel Media have been preparing for this shift for a long time.

Currently, Google has a single index of documents for search. Google’s Gary Illyes announced they plan on releasing a separate mobile search index, which will become the primary one.

Google is going to create a separate mobile index within months, one that will be the main or “primary” index that the search engine uses to respond to queries. A separate desktop index will be maintained, one that will not be as up-to-date as the mobile index.

The news came today during a keynote address from Gary Illyes, a webmaster trends analyst with Google, at Pubcon. Illyes didn’t give a timeline in his talk, but in a follow-up with Search Engine Land, he confirmed that it would happen within “months.”

Google first announced that it was experimenting with the idea of a mobile index last year at SMX East. Since that time, Google’s clearly decided that a mobile index makes sense and is moving ahead with the idea.

It’s unclear exactly how the mobile index will work. For example, since the mobile index is the “primary” index, will it really not be used for any desktop queries? Will it only contain “mobile-friendly” content? How out-of-date will the desktop index be? Desktop usage is now a minority of Google queries but still generates substantial usage.

The most substantial change will likely be that by having a mobile index, Google can run its ranking algorithm in a different fashion across “pure” mobile content rather than the current system that extracts data from desktop content to determine mobile rankings.

We did ask Google for more details, but all it would confirm is the general timing of the change. Stay tuned for more in a few months, it seems.